[Backend] Add ROCm support

[spectrometerHBH]

Depending on this PR: apache/tvm#15464

On 7900 xtx. ROCm 5.6

~/mlc-llm (rocm ✔) ./build/mlc_chat_cli --local-id Llama-2-7b-chat-hf-q4f16_1
Use MLC config: "/home/bohan/mlc-llm/dist/Llama-2-7b-chat-hf-q4f16_1/params/mlc-chat-config.json"
Use model weights: "/home/bohan/mlc-llm/dist/Llama-2-7b-chat-hf-q4f16_1/params/ndarray-cache.json"
Use model library: "/home/bohan/mlc-llm/dist/Llama-2-7b-chat-hf-q4f16_1/Llama-2-7b-chat-hf-q4f16_1-rocm.so"
You can use the following special commands:
  /help               print the special commands
  /exit               quit the cli
  /stats              print out the latest stats (token/sec)
  /reset              restart a fresh chat
  /reload [local_id]  reload model `local_id` from disk, or reload the current model if `local_id` is not specified

Loading model...
Loading finished
Running system prompts...
System prompts finished
[INST]: Hi
[/INST]: Hello! It's nice to meet you. I'm here to help you with any questions or tasks you may have, while always being safe and respectful. Is there something specific you would like to know or discuss? Please feel free to ask me anything, and I will do my best to provide a helpful and positive response.
[INST]: /stats
prefill: 507.3 tok/s, decode: 92.0 tok/s

~/mlc-llm (rocm ✗) ./build/mlc_chat_cli --local-id Llama-2-13b-chat-hf-q4f16_1
Use MLC config: "/home/bohan/mlc-llm/dist/Llama-2-13b-chat-hf-q4f16_1/params/mlc-chat-config.json"
Use model weights: "/home/bohan/mlc-llm/dist/Llama-2-13b-chat-hf-q4f16_1/params/ndarray-cache.json"
Use model library: "/home/bohan/mlc-llm/dist/Llama-2-13b-chat-hf-q4f16_1/Llama-2-13b-chat-hf-q4f16_1-rocm.so"
You can use the following special commands:
  /help               print the special commands
  /exit               quit the cli
  /stats              print out the latest stats (token/sec)
  /reset              restart a fresh chat
  /reload [local_id]  reload model `local_id` from disk, or reload the current model if `local_id` is not specified

Loading model...
Loading finished
Running system prompts...
System prompts finished
[INST]: Hi
[/INST]: Hello! I'm here to assist you with any questions you may have. Please keep in mind that I strive to provide safe and positive responses that are free of harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. If a question does not make sense or is not factually coherent, I will do my best to explain why instead of providing an incorrect answer. If I don't know the answer to a question, I will not provide false information. Is there anything specific you would like to know or discuss?
[INST]: /stats
prefill: 495.7 tok/s, decode: 69.0 tok/s